The heat diffuser plate can be used in the cooker to about 375 to 400 degrees. If you are cooking hotter, then the heat diffuser MUST be removed, and the direct grilling option (Grill Grates) must be used in the cooker.

If you cook at higher than 400 degrees with the heat diffuser plate installed, you may experience warping of the hopper end corners on the plate, but this may also happen during normal usage. This warping may cause temperatures in the cooker to become erratic as the corners will allow a larger volume of heat to reach the thermocouple.

Here is an example of a warped diffuser plate.

There is a very simple fix for this warping. Purchase a piece of 1/4" steel round bar, 19 1/2" in length from your hardware store (do not use galvanized rod, plain untreated metal rod is best). Place the round bar between the top of the diffuser and below the grate rail. This will force the corners back into position and bring your cooker temperatures back to normal. IF YOUR CORNERS ARE NOT WARPED UP, YOU DO NOT NEED TO DO THIS FIX.

Here is a picture illustrating the round bar in place. I foiled the diffuser so that you can see the round bar placement better.

After running the cooker with the rod in place, you may find that after a few cooks, that the rod doesn't fit tightly anymore, and the diffuser holds it shape without it. At this point the rod may no longer be needed, as the metal has tempered and been "trained" to hold its shape.

I turned my YS640 up to 400* for the first time this past Saturday when making a couple 12 pound turkeys. After it cooled I cleaned out the ash and re foiled my heat diffuser I noticed that it had warped it isn't sitting flat anymore. I will be making a trip to the hardware store very soon to get the rod and a piece of angle iron to put over the damper rod to keep the grease from running of it onto my patio. The angle iron length on my cooker is 3 7/8".

So I'm trying to wrap my head around this...My diffuser is slightly warped but the hopper end corners are drooping...not raising up...The round bar solution looks like it would fix a problem where the corners are raising...

Well, I went a bought a 1/4 inch steel rod, cut it to 19 1/2 inches, came home took the Yoder apart to try it out and I need a 1/2 inch rod to have any effect at all. I think 1/2" square stock would be better anyway. It is hard to tell for sure but the rod in the picture is larger than 1/4" maybe not.

My issue with warping seems to be similar to jeetS where that ends are warped downward instead of up. Any ideas on a fix for that circumstance. If necessary I will post a pic.

Please take pictures of the diffuser in place in the cooker, showing the position of the corners on the hopper end and of the center slot. Also, take a picture of the diffuser from the hopper end sitting on a flat surface.

My issue with warping seems to be similar to jeetS where that ends are warped downward instead of up. Any ideas on a fix for that circumstance. If necessary I will post a pic.

Ya mine are definitely warped down....the only issue I have noticed is that the grease runs toward the front and back of the pit before heading toward the grease bucket...this leaves the hottest spot of the heat deflector basically dry and its rusting.

other than that it still functions fine... maybe a bit more air gets around the deflector than it should but I havent noticed any issues yet...

It appears that the center of your diffuser is warped up, but the gap between the heat diffuser plate and the grate rails looks OK. Warping like this should not affect the performance of the cooker. The warping that does affect the performance of the grill, is where the corners warp up to the point of allowing too much heat and air flow direct access to the thermocouple. I would continue to use the cooker without worry. if you have further concerns, please send an email to customerservice@yodersmokers.com.

to add to this, just as a point of reference, I always center the heat diffuser front to back and snug it up tight to the hopper end wall (being careful of the thermocouple wire). I find that this not only helps temperatures across the grate, but helps to keep the ash below the plate, for the very small amount that potentially could find its way up the hopper wall.

I just measure mine. On the back corner it is about 1/4" raised but on the front corner it in nearly 1 full inch raised. is this allowable or should I also be thinking about retro-fitting. I too have never had the diffuser in at over 350 so am a little concerned seeing my pit was bought last July.

westhemess wrote:I just measure mine. On the back corner it is about 1/4" raised but on the front corner it in nearly 1 full inch raised. is this allowable or should I also be thinking about retro-fitting. I too have never had the diffuser in at over 350 so am a little concerned seeing my pit was bought last July.

I would suggest putting in the 1/4" rod. This warping is normal for the metal plate as it "cures" in the cooker, and in a very small number of cases, can be worse than normal. As any metal heats and cools, it expands and contracts until it finds its zen position. The rod "trains" the metal to hold the required shape.

For the small number that have this warping issue, the rod is a very simple, cheap and easy DIY fix.

My new plate came with the upgrades as a replacement for the old diffuser. I am confused as to why the quality of the new diffuser is so much worse than my old one. I had zero warping problems with the old one. Could someone also tell me why there was a replacement diffuser made? Mine is sagging in the middle. I will take pictures. My temperatures are so widely fluctuating I thought it was my computer. I will also be ordering a new Igniter Rod. I am not sure if this is connected to the heat soaring or not. Coincidence? Maybe.